Rotary combustion engine apex seal lubrication

ABSTRACT

A rotary combustion engine having porous plugs in the rotor that meter oil from the interior of the rotor directly to the apex seals and reed valves that in response to combustion pressure close the porous plugs.

ited States Patent 1191 Walters 1 Dec. 2, 1975 1 1 ROTARY COMBUSTIONENGINE APEX SEAL LUBRICATION [75] Inventor: Leslie K. Walters,Rochester, Mich.

[73} Assignee: General Motors Corporation,

Detroit, Mich.

22 Filed: July 10, 1974 211 Appl. No.:487,172

[52] U.S. Cl 418/91; 418/122 [51] Int. C1. ..F01C 19/02; F01C 21/04;

F04C 27/00 [58] Field of Search 418/91-94,

[56] References Cited UNITED STATES PATENTS Paschke et a1 418/913.261.334 7/1966 Paschke 418/123 FOREIGN PATENTS OR APPLICATIONS 982,9482/1965 United Kingdom 418/124 933583 8/1963 United Kingdom 418/123Primary Examiner-John .l. Vrablik Attorney. Agent, or FirmRorna1d L.Phillips [57 ABSTRACT A rotary combustion engine having porous plugs inthe rotor that meter oil from the interior of the rotor directly to theapex seals and reed valves that in response to combustion pressure closethe porous plugs.

2 Claims, 3 Drawing Figures US. Pmm Dec. 2, 1975 3,923,434

ROTARY COMBUSTION ENGINE APEX SEAL LUBRICATION This invention relates torotary engine apex seal lubrication and more particularly to direct apexseal lubrication through a metering device that is closed by a springvalve in response to combustion pressure.

It is present commercial practice in rotary combustion engines toprovide an oil metering pump that is driven by the engine and controlledwith the engine throttle to meter oil for gas seal lubrication at a ratethat increases with increasing engine load. The oil thus metered is thenmixed with the fuel for delivery to the chamber walls on which the sealsslide. In an effort to provide a more efficient seal lubricationarrangement, there has been proposed direct apex seal lubrication usingoil from inside the rotor as in U.S. Pat. No. 3,261,334 and copendingU.S. application Ser. No. 400,365 now US. Pat. No. 3,884,601 which isassigned to the assignee of the present invention. And now it has beenfound that with the present commercial method of apex seal lubricationwhich coats the entire walls of the chambers, this oil coating canabsorb excessive hy drocarbons during combustion and later release themduring exhaust. Thus, there is added impetus for an efficient, readilymanufacturable and durable arrangement that will provide directlubrication of the apex seals using oil from the interior of the rotorbut without allowing the combustion pressure to back-pressure this oilsupply.

In the present invention there is provided in the bottom of each apexseal slot in the rotor one or more porous plugs of predeterminedporosity which meter oil from the interior of the rotor directly to theapex seals. In addition, a simple reed valve between the normal apexseal spring and the bottom of the apex seal slot responds to combustionpressure to close each plug to prevent this pressure fromback-pressuring the oil in the rotor. Thus, the desired oil metering atvery low rates is provided by inserts which can be more readilymanufactured yet are more durable as compared, for example, with adrilled orifice. Furthermore, the reed valve is independent of the apexseal spring so that its responsiveness to accomplish the desired effectcan be closely predicted and controlled without affecting the apex sealspring.

An object of the present invention is to provide a new and improvedrotary combustion engine apex seal lubrication arrangement.

Another object is to provide a seal lubrication arrangement on the rotorin a rotary combustion engine that meters oil directly to spring biasedapex seals on the rotor through porous plugs which are closed by springvalves in response to combustion pressure.

These and other objects of the present invention will become moreapparent from the following description and drawing in which:

FIG. 1 is a view with parts in section and some parts shownschematically of a rotary combustion engine having apex seal lubricationarrangements according to the present invention.

FIG. 2 is a view taken along the line 22 in FIG. 1.

FIG. 3 is an enlarged view taken from FIG. 1 of one of the apex seallubrication arrangements.

The seal lubrication provided according to the pres ent invention isparticularly. suited for use in a rotary combustion engine of theplanetary type such as shown in FIGS. 1 and 2. The engine comprises ametal housing 10 which in a single rotor arrangement has basically threeparts, namely a rotor housing 12 having an inwardly facing innerperipheral wall 14 and a pair of end housings 16 and 18 having parallel,oppositely facing, spaced inner end walls 20 and 22, respectively. Thehousing parts are secured together by bolts, not shown, and the innerhousing walls 14, 20 and 22 cooperatively provide a cavity 24. As shownin FIG. 2, the peripheral wall is in the shape of a two-lobedepitrochoid or a curve parallel thereto whose center line is indicatedat 26. A crankshaft 28 extends through the cavity 24 and is rotatablysupported in sleeve bearings 30 and 32 which are secured in collars 34and 36 that are bolted to the end housings 16 and 18 as shown in FIG. 1,the crankshaft axis being coincident with the center line 26, parallelto the peripheral wall 14 and at right angles to the end walls 20 and22. The crankshaft 28 is provided in the cavity 24 with an eccentric 38.A hollow metal rotor 40 has a hub 41 having a sleeve bearing 42 securedtherein which is received on the eccentric 38 so that the rotor isthereby supported for rotation about the eccentrics center line 44 whichis thus the rotors axis.

The rotor 40 has the general shape of a triangle with two parallel sidewalls 46 and 48 at right angles to the rotor axis which face and runclose to the end walls 20 and 22, respectively, and a peripheral wall 50having three arcuate outer faces which face the peripheral wall 14 andcooperate therewith and with the end walls 20 and 22 to define threevariable volume working chambers 52. Sealing of these three chambersfrom each other is effected by sealing means comprising three apex seals54 each of which is mounted in an axially extending slot 55 at each apexor comer of the rotor 40 that extends the width thereof. Three arcuateside seals 56 are mounted in accommodating grooves in each rotor sideand extend adjacent the rotor faces between two of the apex seals 54.Three cylindrical corner seals 58 are mounted in cylindrical blind bores59 in each rotor side at the rotor corners with each corner sealproviding sealing between the ends of two side seals and one apex sealas shown in FIG. 2. The apex seals 54 are biased bysprings 60 tocontinuously engage the peripheral wall 14 while the side seals 56 andthe corner seals 58 are biased by springs 61 and 62, respectively, tocontinuously engage the respective end walls 20 and 22 with the completegas seal arrangement acting to seal the working chambers.

With the two-lobed peripheral wall 14 and the three corner rotor 40,each of the working chambers 52 sequentially expands and contractsbetween minimum and maximum volume twice during each revolution in fixedrelation to the housing by forcing the rotor to rotate at one-third thespeed of the crankshaft. This is accomplished by gearing comprising aninternal tooth rotary phasing gear 63 which is fixed in side 48 of therotor concentric with the rotor axis. The gear 63 meshes with anexternal tooth annular stationary phasing gear 64 which is freelyreceived about and is concentric with the crankshaft 28 and is madestationary by being formed integral with the left-hand end of theright-hand collar 36 as shown in FIG. 1. The gear 63 has one andone-half times the number of teeth as the gear 64 to provide therequired speed ratio of 3:1 between the crankshaft and the rotor.

A combustible air-fuel mixture from a suitable carburetor arrangement,not shown, is made available to each working chamber 52 by an intakepassage 66 shown in FIG. 2. Passage 66 extends through the enginehousing and opens to the cavity through aligned ports 67 in the endwalls and 22 that are located on the leading side of cusp 68 of theperipheral wall 14 relative to the direction of rotor rotation indicatedby the arrow in FIG. 2, there being only one such intake port appearingin this view. A single channel or recess 69 is provided in the center ofeach chamber face of the rotor to provide for the transfer of theworking gas part the peripheral walls other cusp 70 while the rotor faceis at or near a top-dead-center position, as shown in FIG. 2, so thatthe chambers are not divided by the cusp 70 at the time when combustionis occurring therein. A spark plug 72 is mounted in the rotor housing 12adjacent the cusp 70 with its electrodes exposed to the passing workingchambers. As the rotor planetates, the working chambers successivelydraw in fuel mixture as the rotor sides radially outward of the sideseals 56 periodically uncover the intake ports 67. The fuel mixture isthen trapped in each working chamber and compressed and when the rotorface of this chamber is in the vicinity of top-dead-center, this mixtureis ignited at the completion of the compression phase, there beingprovided a suitable ignition system, not shown, for applying voltage tothe spark plug at the proper time. Upon ignition of the mixture in eachworking chamber, the peripheral wall 14 takes the reaction forcing therotor to continue rotating while the gas is expanding. The leading apexseal 54 of each of the working chambers eventually traverses an exhaustpassage 74 in the rotor housing on the trailing side of the cusp 68whereby the exhaust products are then expelled to complete the cycle.

Describing now the lubrication of this arrangement, except for theseals, and also the cooling of the rotor, oil from the engine drains toa sump 75 from which it is drawn by a suitable pump 76 powered from theengine crankshaft 28 and then delivered via a delivery line 78 to anaxial oil passage 80 through the crankshaft 28. Radial oil passages 82,84 and 86 in the crankshaft deliver oil from the passage 80 to lubricatethe sleeve bearings 30, 42 and 32, respectively. The hollow rotor 40 isof the so-called I-beam type as shown in crosssection with a centralradially extending rib 89 between the rotors peripheral wall 50 and thehub 41 and with the rotor side walls 46 and 48 extending radially inwardfrom the peripheral wall with annular spaces left between these sidewalls and rotor hub. A radial oil passage 94 in the crankshaft 28delivers oil from the passage 80 radially outward between the right-handside of the eccentric 38 and the left-hand side of the timing gears 63and 64 to the interior of the rotor for cooling. The oil passes from theright to the left side of the central rib 89 via axially extending,angularly spaced holes 96 therethrough with the oil carrying the heatfrom the rotor by passing out the opposite side openings in the rotor toannular cavities 98 and 99 in the respective end walls 20 and 22. Thecavities 98 and 99 are connected to branches of a return line 100 thatdrains to sump 75. A circular oil seal 102 mounted in an accommodatinggroove in each side wall of the rotor so that it is centered on therotor axis in a radial location inward of the side seals 56 engages theopposite housing end wall to prevent the oil from reaching the gasseals.

The engine structure thus far described is of a conventional presentlycommercial type with lubrication of all but the gas seals normallyprovided by the pump 76 feeding oil to the sleeve bearings and the rotorcooled by the oil circulated therethrough. In such an engine, properlubrication of the apex seals 54 is very important and is normallyprovided by an oil metering pump that meters oil to either mix with thefuel prior to its induction into the working chambers or feed throughoil feed ports in the housing directly into the chambers with thismetering controlled to increase with inccreasing engine load to assureadequate seal lubrication with varying engine conditions. Others havetaught that more efficient seal lubrication may be obtained by deliveryof oil from within the rotor directly to the apex seals however theirproposed means for effecting such delivery are generally either not wellsuited to mass production, are not very durable or impose substantialmodifications or material changes for the rotor. These objections areovercome by the present invention which as best shown in FIG. 3 has apexseal lubricant metering means at each apex of the rotor comprising apair of counterbored holes 104 which are located on opposite sides ofthe rib 89 and extend radially through the rotors circumferentiallyextending wall 50 between the interior of the rotor and the bottom ofthe associated apex seal slot 55. A porous plug 106 is mounted in eachof the holes 104 and has a predetermined porosity such that thecentrifugal forces on the body of cooling oil in the rotor are effectiveto force oil to diffuse out through the plugs 106 and thus into the apexseal slot from where the oil eventually migrates to the wear surface ofthe apex seal 54 and also to the corner seals 58 and from there to theside seals 56, this porosity being determined to provide a metered rateof oil for such lubrication that will adequately and efficientlylubricate the seals at minimum speed and load. Then as the engine speedincreases, the metered oil delivered by the porous plugs 106 increasesat an exponential rate with increasing rotor speed as the result of thecentrifugal force to assure good, but not excessive, gas seallubrication over the engines entire speed range.

In the preferred embodiment, the porous plugs 106 are formed of apowdered metal with their predetermined porosity accomplished by thematerial mix and the manufacturing process, the required porositiy thusbeing provided in a manner readily suited to highvolume mass production.A typical type of material mix giving lubricant diffusion porositysuitable for use in the rotary combustion engine environment comprisespredominantly iron with some graphite and lubricant. The powder isbriquetted in the plug shape to a certain green density and then a smallpercentage of copper is infiltrated into the briquetted powdered metalplug during sintering thereof, this percentage of copper being dependenton the green part weight and decreasing with increasing density. Duringsintering, the copper infiltrates the then relatively highly porous plugstructure to fill a high percentage of the interstices yet leave enoughinterconnected voids to produce the desired diffusion rate.

To prevent the combustion pressure that reaches the bottom of the apexseal slot 55 from back-pressuring the oil within the rotor, there isprovided a reed valve 108 made from a flat piece of spring steel that isarranged between the apex seal spring and the bottom of the apex sealslot 55, the reed valve 108 thus actually serving as the seat for theapex seal spring 60 but in no way affecting the operation thereof norpermitting the a apex seal spring to effect its operation. The reedvalve 108 has a tang 110 lanced from its middle which projectsdownwardly into a locator hole 112 in the bottom of the apex seal slot55 'to center the reed valve with its oppositely extending flexibleportions always arranged over the porous oil metering plugs 106. Thespring rate of the reed valve 108 is determined to be sufficiently lowto permit the aforementioned minimum metered oil supply at engine idleby the flexible portions deflecting in response to the centrifugallygenerated pressure on the oil through the porous plugs at this rotorspeed and whenever the pressure on the reed valve from the combustionchambers exceeds a predetermined amount which is less than thecentrifugal fluid pressure developed because of the spring forceopposition to the latter, the reed valve 108 closes on the porous plugs.Thus, the combustion pressure is prevented from affecting the internaloil pressure in the rotor during the time each apex seal slot is exposedto combustion pressure which is once during every rotor revolution.

To illustrate some of the results that have been obtained from actualtests using the structure described, an engine was run for a prescribedtime under similar conditions first with a conventional oil meteringsystem having a pump metering oil to the fuel and then with thelubrication system according to the present invention. In thesecomparative tests, it was found that with the conventional oillubrication metering system, 190 grams of oil were consumed whereas theoil consumption with the direct oiling arrangement according to thepresent invention was only 50 grams or only about onefourth the normalamount of oil consumption. Furthermore, comparative tests also showedboth a substantial improvement in fuel economy and a substantialreduction in hydrocarbons.

The above described embodiment is illustrative of the invention whichmay be modified within the scope of the appended claims.

I claim:

1. A rotary combustion engine comprising an engine housing having aninternal peripheral wall and oppositely facing end walls cooperativelydefining a cavity, a shaft extending through said cavity and end wallsand rotatably supported by said housing, a hollow rotor located in saidcavity and rotatably mounted on said shaft and having apexes that remainclose to said internal peripheral wall as said shaft and rotor rotate,said rotor having a circumferentially extending wall cooperating withsaid peripheral wall of said housing an oppositely facing radiallyextending side walls cooperating with said end walls of said housing toprovide a plurality of chambers between said apexes that are spacedabout and move with said rotor while varying in volume as said rotor andsaid shaft rotate, apex seals mounted in slots in said rotor at saidapexes for engaging said peripheral wall, a spring arranged between thebottom of each said slot and the bottom of the associated apex seal forurging the apex seal outwardly against said peripheral wall, a source ofoil, passage means for delivering the oil to and from the interior ofsaid rotor, said rotor having a central rib therein extending radiallyinwardly from said circumferentially extending wall, and apex seallubricant metering means mounted in said rotor at each said apex formetering oil from the interior of said rotor to the associated apex sealslot without permitting combustion pressure to backpressure the oil insaid rotor whereby oil is effectively delivered directly to the wearsurfaces of the apex seals, each said apex seal lubricant metering meanscomprising a pair of porous plugs mounted in lubricant delivery holes insaid circumferentially extending wall connecting the interior of saidrotor on opposite sides of said rib to the bottom of the associated apexseal slot, said porous plugs having a porosity effective to permit oilto diffuse therethrough as a result of centrifugal forces on the body ofoil within said rotor and at a rate sufficient to adequately lubricatesaid apex seals at minimum rotor speed and load and as a result ofcontinuing centrifugal action on the oil in the interior of said rotorproviding increasing oil delivery to increase the lubrication of saidapex seals with increasing rotor speed, a flat spring valve arrangedbetween each said apex seal spring and the bottom of the associated apexseal slot and extending at opposite ends along flexible portions overthe associated porous plugs for opening the porous plugs only when theoil pressure acting on the porous plug side of the flexible portionsexceeds the gas pressure from said chambers acting on the opposite sideby a predetermined amount.

2. A rotary combustion engine comprising an engine housing having aninternal peripheral wall and oppositely facing end walls cooperativelydefining a cavity, a shaft extending through said cavity and end wallsand rotatably supported by said housing, a hollow rotor located in saidcavity and rotatably mounted on said shaft and having apexes that remainclose to said internal peripheral wall as said shaft and rotor rotate,said rotor having a circumferentially extending wall cooperating withsaid peripheral wall of said housing and oppositely facing radiallyextending side walls cooperating with said end walls of said housing toprovide a plurality of chambers between said apexes that are spacedabout and move with said rotor while varying in volume as said rotor andsaid shaft rotate, apex seals mounted in slots in said rotor at saidapexes for engaging said peripheral wall, a spring arranged between thebottom of each said slot and the bottom of the associated apex seal forurging the apex seal outwardly against said peripheral wall, a source ofoil, passage means for delivering the oil to and from the interior ofsaid rotor, said rotor having a central rib therein extending radiallyinwardly from said circumferentially extending wall, and apex seallubricant metering means mounted in said rotor at each said apex formetering oil from the interior of said rotor to the associated apex sealslot without permitting combustion pressure to backpressure the oil insaid rotor whereby oil is effectively delivered directly to the wearsurfaces of the apex seals, each said apex seal lubricant metering meanscomprising a pair of porous plugs mounted in lubricant delivery holes insaid circumferentially extending wall connecting the interior of saidrotor on opposite sides of said rib to the bottom of the associated apexseal slot, said porous plugs having a pososity effective to permit oilto diffuse therethrough as a result of centrifugal forces on the body ofoil within said rotor and at a rate sufficient to adequately lubricatesaid apex seals at minimum rotor speed and load and as a result ofcontinuing centrifugal action on the oil in the interior of said rotorproviding increasing oil delivery to increase the lubrication of saidapex seals with increasing rotor speed, a flat spring valve arrangedbetween each said apex seal spring and the bottom of the associated apexseal slot and extending at opposite ends along flexible portions overthe associated porous plugs for opening the porous plugs only when theoil pressure acting on the porous plug side of the flexible portionsexceeds the gas pressure from said ter projection projecting radiallyinwardly into a locator hole in the bottom of the associated apex sealslot to maintain the flat spring valve in proper valve relachambersacting on the opposite side by a predetertlonshlp with the associatedPorous P mined amount said flat spring valve also having a cen-

1. A rotary combustion engine comprising an engine housing having aninternal peripheral wall and oppositely facing end walls cooperativelydefining a cavity, a shaft extending through said cavity and end wallsand rotatably supported by said housing, a hollow rotor located in saidcavity and rotatably mounted on said shaft and having apexes that remainclose to said internal peripheral wall as said shaft and rotor rotate,said rotor having a circumferentially extending wall cooperating withsaid peripheral wall of said housing an oppositely facing radiallyextending side walls cooperating with said end walls of said housing toprovide a plurality of chambers between said apexes that are spacedabout and move with said rotor while varying in volume as said rotor andsaid shaft rotate, apex seals mounted in slots in said rotor at saidapexes for engaging said peripheral wall, a spring arranged between thebottom of each said slot and the bottom of the associated apex seal forurging the apex seal outwardly against said peripheral wall, a source ofoil, passage means for delivering the oil to and from the interior ofsaid rotor, said rotor having a central rib therein extending radiallyinwardly from said circumferentially extending wall, and apex seallubricant metering means mounted in said rotor at each said apex formetering oil from the interior of said rotor to the associated apex sealslot without permitting combustion pressure to backpressure the oil insaid rotor whereby oil is effectively delivered directly to the wearsurfaces of the apex seals, each said apex seal lubricant metering meanscomprising a pair of porous plugs mounted in lubricant delivery holes insaid circumferentially extending wall connecting the interior of saidrotor on opposite sides of said rib to the bottom of the associated apexseal slot, said porous plugs having a porosity effective to permit oilto diffuse therethrough as a result of centrifugal forces on the body ofoil within said rotor and at a rate sufficient to adequately lubricatesaid apex seals at minimum rotor speed and load and as a result ofcontinuing centrifugal action on the oil in the interior of said rotorproviding increasing oil delivery to increase the lubrication of saidapex seals with increasing rotor speed, a flat spring valve arrangedbetween each said apex seal spring and the bottom of the associated apexseal slot and extending at opposite ends along flexible portions overthe associated porous plugs for opening the porous plugs only when theoil pressure acting on the porous plug side of the flexible portionsexceeds the gas pressure from said chambers acting on the opposite sideby a predetermined amount.
 2. A rotary combustion engine comprising anengine housing having an internal peripheral wall and oppositely facingend walls cooperatively defining a cavity, a shaft extending throughsaid cavity and end walls and rotatably supported by said housing, ahollow rotor located in said cavity and rotatably mounted on said shaftand having apexes that remain close to said internal peripheral wall assaid shaft and rotor rotate, said rotor having a circumferentIallyextending wall cooperating with said peripheral wall of said housing andoppositely facing radially extending side walls cooperating with saidend walls of said housing to provide a plurality of chambers betweensaid apexes that are spaced about and move with said rotor while varyingin volume as said rotor and said shaft rotate, apex seals mounted inslots in said rotor at said apexes for engaging said peripheral wall, aspring arranged between the bottom of each said slot and the bottom ofthe associated apex seal for urging the apex seal outwardly against saidperipheral wall, a source of oil, passage means for delivering the oilto and from the interior of said rotor, said rotor having a central ribtherein extending radially inwardly from said circumferentiallyextending wall, and apex seal lubricant metering means mounted in saidrotor at each said apex for metering oil from the interior of said rotorto the associated apex seal slot without permitting combustion pressureto backpressure the oil in said rotor whereby oil is effectivelydelivered directly to the wear surfaces of the apex seals, each saidapex seal lubricant metering means comprising a pair of porous plugsmounted in lubricant delivery holes in said circumferentially extendingwall connecting the interior of said rotor on opposite sides of said ribto the bottom of the associated apex seal slot, said porous plugs havinga pososity effective to permit oil to diffuse therethrough as a resultof centrifugal forces on the body of oil within said rotor and at a ratesufficient to adequately lubricate said apex seals at minimum rotorspeed and load and as a result of continuing centrifugal action on theoil in the interior of said rotor providing increasing oil delivery toincrease the lubrication of said apex seals with increasing rotor speed,a flat spring valve arranged between each said apex seal spring and thebottom of the associated apex seal slot and extending at opposite endsalong flexible portions over the associated porous plugs for opening theporous plugs only when the oil pressure acting on the porous plug sideof the flexible portions exceeds the gas pressure from said chambersacting on the opposite side by a predetermined amount said flat springvalve also having a center projection projecting radially inwardly intoa locator hole in the bottom of the associated apex seal slot tomaintain the flat spring valve in proper valve relationship with theassociated porous plugs.